Best possible answers collected so far for [Regex golf](http://regex.alf.nu/). === WARNING: SPOILERS ===

regex_golf.md

See Also:

• HN Post
• Regex Golf Answers (Gist)
• Best known Regex Golf solutions (Gist)
• Regex Golf (reddit)

Normal

Level	Score	Regex	Credit
Warmup	207	foo
Anchors	208	k$
Ranges	202	^[a-f]*$
Backrefs	201	(...).*\1	gorhill (HN)
Abba	195	^(?!.*(.)\1)|ef	BeniaminK (GH)
A man, a plan	177	^(.)[^p].*\1$	hyp0 (HN)
Prime	286	^(?!(..+)\1+$)	josephlord (HN)
Four	199	(.)(.\1){3}	chrismorgan (HN) / MereInterest (HN)
Order	199	^.{5}[^e]?$	ekke (HN)
Triples	596	00($|3|6|9|12|15)|4.2|.1.+4|55|.17	alexandrosm (GH)
Glob	397	ai|c$|^p|[bcnrw][bnopr]	nwellnhof (HN)
Balance	454	.{37}|^(<(..(?!<.>$))*>)*$	Davidebyzero (GH)
Powers	93	^(?!(.(..)+)\1*$)	plby (GH)
Long count	256	((.+)0\2+1){8}	Davidebyzero (GH)
Alphabetical	317	.r.{32}r|a.{10}te|n.n..	alexandrosm (GH)
Powers 2	88	^(?!((xxx)+x|xx|)\1*$)	muxrwc (GH)
Total	4075
Subtraction	180	^(.+)(.+) - \1 = \2$	jonathanmorley (GH)
Typist	181	^[adresbtcfxzgvw]+$	jonathanmorley (GH)

Hard Mode

Level	Score	Regex	Credit
Warmup	207	foo
Anchors	206	ick$	Davidebyzero (GH)
Ranges	202	^[a-f]*$
Backrefs	201	(...).*\1	gorhill (HN)
Abba	193	^(?!.*(.)(.)\2\1)	chingjun (HN) / josephlord (HN)
A man, a plan	150	^(.?)(.?)(.?)(.?)(.?)(.?).?\6\5\4\3\2\1$	jonathanmorley (GH)
Prime	284	^(?!(xx+)\1+$)xx	Davidebyzero (GH)
Four	199	(.)(.\1){3}	chrismorgan (HN) / MereInterest (HN)
Order	156	^a*b*c*d*e*f*g*h*i*j*k*l*m*n*o*p*q*r*s*t*u*v*w*x*y*z*$	Davidebyzero (GH)
Triples	524	(?=((.*?[147]){3})*((.*?[147]|){2}))(?=((.*?[258]){3})*((.*?[258]|){2}))^.*$(\3\7|(?!\3|\7)\4\8|(?!\4|\8))	teukon (GH)
Glob	297	ai|c$|^p|[bcnrw][bnopr]	nwellnhof (HN)
Balance	443	^(<(<(<(<(<(<(<>)*>)*>)*>)*>)*>)*>)*$	gkucmierz (GH)
Powers	93	^(?!(.(..)+)\1*$)	plby (GH)
Long count	239	^((?=(\S*)0).{4} (?=\2[1]))+1+$	Davidebyzero (GH)
Alphabetical	282	^(?!.*\b(.*)(e|(n|r|(s|t))).* \1(a|(?!\3)[en]|(?!\4)[rs]))	teukon (GH)
Powers 2	-12	^(?!((xxx)+x|xx|)\1*$)	muxrwc (GH)
Total	3664
Subtraction	180	^(.+)(.+) - \1 = \2$	jonathanmorley (GH)
Typist	180	^[adresbtcfxzgvwq]+$	jonathanmorley (GH)

Subtraction ^(x+)(.+)- \2= \1$, no full space

New level: It never ends – $ not allowed
3 chars: u\b